1. Field of the Invention
The present invention relates to improvements in a roof panel mounting structure through which a roof panel of a vehicle is fixed to a roof rail forming part of a vehicle body.
2. Description of the Prior Art
Hitherto a roof panel mounting structure as shown in FIG. 3 of the drawing of the present application has been proposed as disclosed, for example, in Japanese Utility Model Provisional Publication No. 61-117775. In connection with this roof panel mounting structure, a vehicle body 1 includes a hollow roof rail 4' disposed below and along the roof panel 2'. The roof rail 4' is constituted by inner and outer panels 5', 6' which are joined to each other to form a generally closed cross-section. The roof panel is formed of plastic and integrally formed at its inner surface with a boss section 8' which projects downwardly and toward the outer panel 6' of the roof rail 4'. The boss section 8' is formed with a threaded hole 7' into which a bolt 9' is screwed passing through the outer panel 6', so that the roof panel 3 is fixedly secured to the outer panel 6' of the roof rail 4'.
However, with such a conventional roof panel mounting structure, the vertical length L' of the boss section 8 must be sufficiently large to securely retain the bolt 9. According to the present inventors' estimation, it is desirable that the vertical length L' of the boss section is at least 18 mm in order to securely retain the bolt 9'. Accordingly, assuming that the length L' of the boss section 8' is made sufficiently large without changing the height 8' of the roof panel 3' and the amount of displacement of the roof rail 4' toward the inside of a passenger compartment R', the outer panel 6' of the roof rail 4' is partly depressed downwardly at a portion opposite to the boss section 8' in order to receive the boss section 8'. This partly decreases the cross-sectional area S' of the roof rail 4', thereby lowering the rigidity of the roof rail 4'.
It is a matter of course that a sufficient length of the boss section 8' can be ensured without decreasing the cross-sectional area S' of the roof rail 4' if the roof rail 4' protrudes into the passenger compartment R', thereby reducing the effective volume of the passenger compartment R'.